Distillation. The process of distilation is one which is used for separating liquids from each other which boil at dif-if heat. In domesticeconomy, it is most frequently employed to obtain sprit, more or less flavoured, or scented, with some volatile essential oil, The appa-ratus commonly used is the Still, for boiling the liquid to generate the vapour, and a long spirally-twisted tube termed the Worm, which is placed in a tub of cold water, and through which the steam pastes to he condensed. The worm is the most objectionable part of the modern still; its great evil is the difficulty with which it is cleaned, so as to prevent one strung-flavoured substance spoiling those which are distilled afterwards. If the coils of the worm are not very numerous, a bullet, with a string attached, may be passed through it, and a sponge or small bottle-brush, fastened to the string, may be worked backwards and forwards; but if there are several coils, it will be found impossible to do this, from the resistance caused by friction. In this case, the only plan is to close one end of the worm with a cork, and fill it with a solution of caustic alkali, a lowing it to remain for some hours, and rep ating the application with fresh liquid, it be required.
In Germany, the worm is being superseded by an excellent condenser, which is so superior that we are induced to give a sketch of it, hoping that it may lead to its adoption in this country. The vapours from the still pass into the tube A (fig. 1), by which they are conducted into B, a hollow globe, made to unscrew at its centre. The vapours, passing along the tubes C, are condensed, and the distilled liquid drops from 1). The pipe E should convey a constant stream of cold water to the bottom of the tub, and this, rising as it is warmed by abstracting heat from the tubes and globe, should escape by F. All the tubes being straight, it is obvious that they can be readily cleaned from their ends. In the laboratory, distilling is most frequently performed with vessels termed retorts, or even from flasks; but as these are not very applicable to domestic purposes, we pass them over.
In domestic practice, the still is usually employed to obtain some water or spirit fla-voured with essential oil, or the oil itself, and the process should be slightly modified so as to suit each case. The vegetable Bub-stance should not be placed on the bottom of the still itself, at in that ease it might become burnt, and so give an unpleasant flavour to the whole; but a bottom of wicker-work should be placed in the still in the first instance for it to rest upon, or a perforated board. The substance to be distilled should be placed in the still, covered with water, for some hours before the fire is lighted ; no more water being added than sufficient to cover it, if the preparation of oil is the object.
Herbs, for distilling, should be collected on a dry day, and - unless the oil resides in the seeds, as in the case of caraway, anise, etc, or in the flowers, as in the rose, lavender, etc. - iust before the flowers have opened, as at that period there is the greatest quantity of essential oil in the plant All plants cultivated for distillation should be grown in a situation where they can receive a full amount of sun-light, as shade or darkness very much tend to prevent the formation of essential oil.
The liquid which comes out of the worm is a mixture of water highly-flavoured with the substance, and some undissolved oil. This latter is sometimes heavier and sometimes lighter than water, either sinking or floating; in the latter case the oil may be readily separated by filling a bottle with the mixture, and, when the oil is collected at the top, carrying it off by a few threads of cotton placed as in fig. 2, taking care that they are moistened with oil before arranging them ; the cotton acts as a syphon, and removes the whole of the oil. If the object of the operation is to obtain the oil and not the distilled water, the later should be preserved, and used again and again with fresh herbs; because, having in the first operation dissolved up as much oil as it is capable of doing, it causes no loss in the subsequent distillations.
It may, perhaps be thought that our article is incomplete, from our not giving any particular directions as to the manufacture of spirits, both as regards the first fermentation and subsequent distillation ; but our readers should bear in mind that the manufacture of spirit is illegal, and the result is most frequently a heavy fine and imprisonment, to which we have no wish that our articles should be introductory.